Many occasions arise that require electronic access control of different types of cabinets, entryway doors, carts, tool boxes, and other types of boxes, hereafter regardless generally of their compositions, materials, or configurations collectively referred to as an enclosure or cabinet. Such enclosures or cabinets may be provided with doors and/or may also include drawers.
The need for access control usually arises from the lack of security often provided by typical lock and key mechanisms. For example, a mechanical key may be lost or stolen. Once such a lost or stolen key has been surreptitiously obtained by an unauthorized individual, such individual in possession of such key may easily access the secured enclosure to either steal its contents or, as in the case of secured medical records or other confidential documents, view its contents. Further, when such enclosures or cabinets are accessed, there is typically no record that it has been accessed, let alone who accessed it or when such access took place.
Such shortcomings of keyed mechanical locks have contributed to the creation of the specialized field of electronic access control.
Typically, electronic access control may correspond to a three part system, including, for example: (1) a credential reader, (2) a microprocessor based control circuit, and (3) an electronic latch to mechanically open or unlock the enclosure being secured by the access control system.
Credential readers may include, but are not limited to: keypads, magnetic stripe card readers, proximity card readers, “ibuttons,” smart card readers, and/or bar code card readers. In the recent past, there has been significant progress in the field of biometrics that includes, but is not limited to, the ability to reliably read and discern an individual's fingerprints, handprints, and retina and/or facial features.
Generally speaking, credential and/or biometric readers convert their applicable credential or biometric features, respectively, into a binary number. A microprocessor based system then reads and analyzes such binary number. Such systems are typically either standalone (attached to the reader) or networked (attached to many readers). Typically, they may read the binary number that corresponds to the potential entrant's credential or biometric features and compare it to a list of approved binary numbers. In such fashion, the microprocessor based system determines if the potential entrant has the right to access the enclosure or cabinet being secured by the access control system.
If the microprocessor based system determines that the subject credential or biometric feature under consideration is valid, access is granted to the enclosure. Typically, such is accomplished by the microprocessor turning on an electronic control circuit corresponding to a solid state devices or relays which in turn provide a useable electrical voltage to open an electronic latch mechanism. There are generally speaking two primary styles of electronic latch mechanisms: slam latches and dead bolt latches.
Slam latches have a spring loaded locking feature or slam bolt, allowing for the door of the enclosure to be locked by simply pushing or “slamming” the door closed. The slam bolt is easily pushed into the latch body and is provided with a spring return.
Typically, one side of such a slam bolt is provided with a cam surface. The slam latch in general terms is mounted to the interior door surface of a given enclosure such that the cam surface strikes the enclosure frame, which in turn drives the latch's slam bolt into the latch body as the door is closed. Such action charges a return spring. Typically, the inside of the enclosure frame is provided with a locking surface against which the slam bolt locks. Once the enclosure door is closed, the charged return spring extends the slam bolt, locking the enclosure.
Dead bolt latches utilize a fixed dead bolt without means of a spring return. Such types of latches instead require the electronic control circuit to actuate a motor or solenoid to alternately retract and/or extend the dead bolt in order to provide the locking (or unlocking) action. In other words, a locking action is not “automatic” when the enclosure door is closed.
The dead bolt in the above-referenced type of latch mechanism is typically provided with a square or rectangular end (though alternatives may be practiced). A latch utilizing such type of bolt is generally speaking in at least one sense more secure than a slam latch because it needs to receive a credentialed (i.e., authorized) signal in order for the dead bolt to be retracted. In comparison, the bolt of a slam latch may simply be pushed in. Such “pressing in” action can be done by a thief after employing dishonest means to access the enclosure being secured by the slam bolt. However, the corresponding adverse or negative aspect of the dead bolt type latch is that an enclosure door cannot simply be slammed closed. The latch must receive a signal from the access control system to extend the dead bolt at the correct time.
It is a fairly common occurrence in the field that such latches will have some locking force applied to them in a direction which is perpendicular to the bolt surface. Such force can be the result of a variety of influences and/or conditions, for example, improperly installed latches, racked or twisted cabinets, swollen door materials (for example, wood), articles inside the enclosure falling against the inside of the door, and/or from an enclosure being “over stuffed”. Such a “pre-load” on the latch bolt may in some instances be relatively significant, for example, on the order of several pounds.
The prime mover in the types of latches presently addressed are typically either a solenoid or a motor/gear train combination. Solenoid based latches having equal strength to a given motor/gear train based latch are significantly larger and heavier than such “equivalent” motor/gear train design. Latches constructed in accordance with the present subject matter are motor based.
Motor/gear train based slam latches present a design challenge in that during the slam action, the locking bolt needs to be disconnected from the gear train. If such aspect is not properly provided or accomplished, it may have a detrimental affect on the reliability of the gear train and latch.
It is further desirable from a manufacturing and business point of view to have a latch that is easily assembled as either a slam latch or a dead bolt latch configuration, depending on the simple addition/deletion of a minimal number of parts.
While various implementations of enclosure locking mechanisms have been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.